Generally, a vacuum assisted closure (VAC) therapy or a negative pressure wound therapy (NPWT), being classified as a kind of adjuvant physical therapy, is operated by applying a negative pressure pump to a patch of a bio-compatible porous wound dressing covering a wound for forming a negative pressure inside the wound, by that, as the negative pressure will cause the volume of the porous wound dressing to contract and consequently force the wound to close as well as the shear stresses of the contracted porous wound dressing will cause a drag to the boundary tissues of the wound for enhancing cell division and proliferation, the healing of the wound can be accelerated. It is noted that the application of the negative pressure through the porous wound dressing not only can improve the growth of blood vessels and the local blood circulation as the flowing of tissue fluid between cells can be enhanced, but also it can prevent the happening of edema and inflammation, create a moist healing environment with good wound protection as it can draw cellular waste and excess tissue fluid out of the wound, and thus the healing time of the wound can be reduced.
Generally, a conventional NPWT system comprises: a patch, for covering and sealing a wound; a bio-compatible porous wound dressing, for placing inside the wound; a drainage tube, placed adjacent to or inserted in the dressing for connecting the wound to a spent liquid container; and a connection tube, connecting the spent liquid container to a vacuum source; by which a negative pressure is applied to the wound for draining spend liquid from the wound to the spent liquid container. As the negative-pressured drainage tube is directly inserted into the dressing that is placed inside the wound, there will be some components of the NPWT system to be disposed on top of the wound forming an obstructive structure. Such obstructive structure not only may adversely affect the airtightness of the wound as the patch may be deformed or even damaged by the pressing thereof, but also it may sometimes cause clogging in the drainage tube and thus affect the healing of the wound. In addition, when the wound is formed on the back or foot of a patient, such as diabetic foot lesions or bedsores, such obstructive structure may cause discomfort to the patient.
There are already some studies trying to improve the conventional NPWT system. One of which is a drainage system, disclosed in U.S. Pat. No. 6,626,891, entitled “Drainage system to be used with an open wound, an element which is used thereby for placing a drainage tube or hose and a method of using said drainage system”. The aforesaid drainage system is consisted of: a block of a foamy material, placed on a wound for absorbing wound fluid; a plate-shaped member, configured with a thickening in a manner that there is a hollow space formed inside the thickening; and a foil, affixed to the upper side of plate-shaped member while capable of adhere to the skin surrounding the wound; wherein the hollow space in the thickening is enabled to communicate with the block through a plurality of opening, and is connected to a drainage tube through an open formed on the thickening while the drainage tube is connected to a suction pump. Thus, it will be apparent that the wound fluid can be withdrawn out of the wound through the foamy block, the openings formed on the plate-shaped member, the hollow space inside the thickening and the drainage tube. However, as the plate-shaped member must be formed with a specific hardness and thickness and also as the thickening and the drainage tube are placed at a position about the center of the wound, such configuration not only may adversely affect the airtightness of the wound as the foil may be easily detached from the plate-shaped member by the pressing thereof, but also it may sometimes cause clogging in the drainage tube since it can be bended easily during usage or cause the drainage tube to be pull loose by careless usage. In addition, it can cause discomfort to the patient as it is pressed directly on the wound.
Another such study is a wound therapy device disclosed in U.S. Pat. No. 7,273,054, entitled “Surgical drape and head for wound treatment”. The aforesaid wound therapy device is basically a flat head having a plurality of column-like projections formed on a side thereof while having a connector formed on another side thereof in a manner that it penetrates the flat head and is provided for connecting to a suction pump through a drainage tube. By covering the side of the flat head where the column-like projections are formed on a dressing fitted inside a wound as the flat head is blanketed under a flexible film that is adhere to the skin surrounding the wound, the wound fluid can be withdrawn out of the wound through the dressing, the apertures formed between the column-like projections, the connector and the drainage tube. Similar to the device disclosed in U.S. Pat. No. 6,626,891, As the formation of the column-projections on the flat head causes the flat head must be formed with a specific hardness and thickness and also as the connector and the tube are placed at a position about the center of the wound, such configuration not only may adversely affect the airtightness of the wound as the flexible film may be easily detached from the flat head by the pressing thereof, but also it may sometimes cause clogging in the drainage tube since it can be bended easily during usage or cause the drainage tube to be pull loose by careless usage. In addition, it can cause discomfort to the patient as it is pressed directly on the wound.
One another such study is a wound therapy device disclosed in U.S. Pat. No. 7,128,735, entitled “Reduced pressure wound treatment appliance”. The aforesaid wound therapy device uses a funnel-like overlay to mask a wound so that the wound fluid can be withdrawn through a drainage tube fitted inside the overlay that is connected to a suction pump. Despite of the improvement over the airtightness performance, the bulky overlay can cause great trouble and discomfort to the movement of a patient using the treatment device. In addition, the drainage tube can be clogged as it is easily being bended in usage.
From the above description, it is noted that there is in need of a NPWT apparatus without the aforesaid disadvantages of poor airtightness performance, patient discomfort and the clogging of tubes.